(Uncorrected OCR)
Abstract of thesis entitled Experimental Study of A Modified Flat Dilatometer under Plane Strain Condition
submitted by
Deepthi de Silva Udakara
for the degree of Doctor of Philosophy at the University of Hong Kong
in February 2000
This thesis describes the development of a new form of flat plate dilatometer and the construction of a plane strain testing facility that is particularly suited to the confirmation of some of the capabilities of the modified device and similar blade like devices.
The specimen is rectangular in cross section and, in order to simulate the actual field conditions in the laboratory, the specimen is contained in a box shaped rubber membrane. The two ends are supported by rigid steel plates. The open sides of the membrane provide for variable lateral boundary conditions while the end plates are used as restraint to ensure plane strain conditions. The test results indicated that uniform and consistent sand specimens could be prepared at different relative densities using the sand raining method.
The modified dilatometer has been specially designed to reduce penetration disturbance in the vicinity of the test diaphragm. In addition, this presents the opportunity to measure directly a range of characteristics associated with stress-strain response because the soil adjacent to the diaphragm is essentially undisturbed at the start of the test. The results showed the capability of this new device to measure sand properties such as small strain shear modulus and lateral stress. The measured lateral stresses by this new device were significantly improved over the values obtained by the standard dilatometer blade due to the reduced penetration disturbance. Also, the initial shear modulus was found to be proportional to the confining pressure in sand.